Process for making microporous membranes from poly(etheretherketone)-type polymers

Abstract

A method of preparing a microporous membrane from unsulfonated poly(etheretherketone)-type polymers.

What is claimed is: 
     
       1. A process for preparing a microporous poly(etheretherketone)-type membrane comprising the steps of: A. forming a mixture of: (i) at least one unsulfonated poly(etheretherketone)-type polymer, and   (ii) a plasticizer comprising at least one organic compound capable of dissolving at least about 10 weight percent of the poly(etheretherketone)-type polymer as the extrusion or casting temperature;   B. heating the mixture to a temperature at which the mixture becomes a homogeneous fluid;   C. extruding or casting the homogeneous fluid under conditions such that a membrane is formed;   D. quenching or coagulating the membrane by passing the membrane through at least one zone under conditions such that the membrane solidifies; and   E. leaching the membrane by passing the membrane through at least one zone under conditions such that at least a portion of the plasticizer for the poly(etheretherketone)-type membrane is removed from the membrane; wherein before leaching, during leaching, after leaching, or a combination thereof, the membrane is drawn to increase the flux of fluid through the membrane, while the membrane is at a temperature above about 25° C. and below the melting point of the poly(etheretherketone)-type polymer or the depressed melting point of the poly(etherethereketone)-type polymer and plasticizer mixture.     
     
     
       2. The process of claim 1 wherein the plasticizer comprises at least one solvent consisting predominantly of carbon and hydrogen and optionally oxygen, nitrogen, sulfur, halogen, and mixtures thereof, wherein the solvent has a molecular weight of between about 160 and about 450, contains at least one six-membered ring structure, and possesses a boiling point of between about 150 and about 480° C. 
     
     
       3. The process of claim 2 wherein the plasticizer comprises at least one solvent selected from the group consisting of diphenic acid, N,N-diphenylformamide, benzil, anthracene, 1-phenylnapththalene, 4-bromobiphenyl, 4-bomodiphenylether, benzophenone, 1,-benzyl-2-pyrrolidinone, o,o'-biphenol, phenanthrene, triphenyl-methanol, triphenylmethane, triphenylene, 1,2,3-triphenylbenzene, diphenylsulfone, 2,5-diphenyloxazole, 2-biphenylcarboxylic acid, 4-biphenylcarboxylic acid, m-terphenyl, 4-benzoylbiphenyl, 2-benzoylnapthalene, 3-phenoxybenzyl alcohol, fluoranthene, 2,5-diphenyl-1,3,4-oxadiazole, 9-fluorenone, 1,2-dibenzoylbenzene, dibenzoylmethane, p-terphenyl, 4-phenylphenol, 4,4'-dibromobiphenyl, diphenylphthalate, 2,6-diphenylphenol, phenothiazine, 4,4'-dimethozybenzophenone, 9,10-diphenylanthracene, pentachlorophenol, pyrene, 9,9'-bifluorene, a mixture of terphenyls, SANTOWAX R® mixed terphenyls, a mixture of partially hydrogenated terphenyls, THERMINOL 66® partially hydrogenated terphenyls, a mixture of terphenyls and quaterphenyls, THERMINOL 75® mixed terphenyls and quaterphenyls, 1-phenyl-2-pyrrolidinone, 4,4'-isopropylidenediphenol, 4,4'-dihydroxybenzophenone, quaterphenyl, and mixtures thereof. 
     
     
       4. The process of claim 3 wherein the plasticizer further comprises at least one non-solvent consisting predominantly of carbon and hydrogen and optionally oxygen, phosphorus, silicon, nitrogen, sulfur, halogen, and mixtures thereof, wherein the non-solvent has a molecular weight of between about 120 and about 455 and possesses a boiling point of between about 150 and about 480° C. 
     
     
       5. The process of claim 4 wherein the plasticizer comprises at least one non-solvent selected from the group consisting of 1,3,5-triphenylbenzene, tetraphenylmethane, tetraphenylsilane, diphenylsulfocide, 1,1-diphenylacetone, 1,3-diphenylacetone, 4-acetylbiphenyl, 4,4'-diphenylbenzophenone, 1-benzoyl-4-piperidone, diphenyl carbonate, bibenzyl, diphenylmethylphosphate, 1-bromonapthalene, 2-phenoxybiphenyl, triphenylphosphate, cyclohexylphenylketone, 1,4-dibenzoylbutane, 2,4,6-trichlorophenol, mineral oil, paraffin oil, petroleum oil, MOBILTHERM 600® heat transfer oil, MOBILTHERM 603® heat transfer oil, MOBILTHERM 605® heat transfer oil, butyl stearate, 9-phenylanthracene, 2-phenylphenol, 1-ethoxynaphthalene, phenylbenzoate, 1-phenyldecane, 1-methoxynaphthalene, 2-methoxynaphthalene, 1,3-diphenoxybenzene, 1,8-dichloroanthraquinone, 9,10-dichloroanthracene, polyphosphoric acid, 1-chloronaphthalene, diphenylether, 1-cyclohexyl-2-pyrrolidinone, hydrogenated terphenyl, HB-40® hydrogenated terphenyl, dioctylphthalate, 5-chloro-2-benzoxazolone, dibenzothiophene, diphenylsulfide, diphenylchlorophosphate, fluorene, sulfolane, methyl myristate, methyl stearate, hexadecane, dimethyl phthalate, tetraethylene glycol dimethylether, diethylene glycol dibutylether, docasane, eicosane, dotriacontane, 2,7-dimethoxynaphthalene, 2,6-dimethoxynaphthalene, o-terphenyl, 1,1-diphenylethylene, epsilcaprolactam, thianthrene, silicone oil, DC-704® silicone oil, DC-710® silicone oil, and mixtures thereof. 
     
     
       6. The process of claim 3 wherein the poly(etheretherketone)-type polymer is selected from the group consisting of poly(etherketone), (poly(aryletherketone), poly(etherketoneketone), poly(etheretherketoneketone), poly(etherketoneetherketoneketone), and mixtures thereof. 
     
     
       7. The process of claim 6 wherein the amount of poly(etheretherketone)-type polymer in the polymerplasticizer mixture is between about 10 and about 90 weight percent 
     
     
       8. The process of claim 7 wherein the membrane is drawn at a temperature of between about 25 and about 360° C. 
     
     
       9. The process of claim 8 wherein the membrane is drawn to a draw ratio of between about 1.1 and about 10. 
     
     
       10. The process of claim 9 wherein the homogeneous fluid is extruded at a temperature of between about 150 and about 400° C. 
     
     
       11. The process of claim 10 wherein the membrane is quenched or coagulated at a temperature of between about 0 and about 150° C. 
     
     
       12. The process of claim 10 wherein the quench zone comprises a gaseous environment. 
     
     
       13. The process of claim 11 wherein the membrane is leached at a temperature of between about 0 and about 200° C. 
     
     
       14. The process of claim 13 wherein the leach zone comprises a liquid selected from the group consisting of toluene, xylene, acetone, water, an acid or alkali aqueous solution, and chlorinated hydrocarbons. 
     
     
       15. The process of claim 13 wherein the membrane is useful for ultrafiltration or microfiltration. 
     
     
       16. The process of claim 15 wherein the membrane possesses a porosity in the range of about 10 to about 90 percent. 
     
     
       17. The process of claim 16 wherein the mean pore size of the membrane is in the range of about 5 to about 1000 Angstroms for ultrafiltration and about 0.02 to about 10 microns for microfiltration. 
     
     
       18. The process of claim 17 wherein the membrane possesses a nitrogen flux of at least about ##EQU19## 
     
     
       19. The process of claim 18 wherein the membrane possesses a water flux of at least about ##EQU20## 
     
     
       20. The process of claim 1 which further comprises the additional step of: F. before leaching, after leaching, before drawing, after drawing, or a combination thereof, annealing the membrane by exposing the membrane to a temperatures above the glass transition temperature of the polymer or the polymer and plasticizer mixture and about 10° C. below the melting point of the polymer and plasticizer mixture for a period of time between about 30 seconds and about 24 hours.